Visualizer treeview

The visualizer shows the various objects that make up the expression tree, in a treeview control:

The emphasis is on displaying the structure of the expression tree:

• Not every property becomes a child node; only specific types which are part of the expression tree's structure, such as Expression and CaseBlock
• Properties which return collections -- LambdaExpression.Parameters, Block.RuntimeVariables -- are not rrendered as child nodes. Instead, the individual elements of the collections are rendered as child nodes -- Lambda -> Parameters[0] instead of Lambda -> Parameters -> [0]